During operation of a gas turbine engine, a turbine wheel typically rotates at high speeds in a high temperature environment. The turbine wheel includes a disk that supports a plurality of turbine blades. In many cases, a hub portion of the disk is exposed to temperatures of about 535° C., while a rim portion of the disk is exposed to higher temperatures, such as about 815° C. or higher. Because of these differences in operating conditions, hubs have been configured to have the qualities of high tensile strength and high resistance to low cycle fatigue, while rims have been configured to have the qualities of high stress rupture and creep resistance. Such hubs fall into the category of dual microstructure components.
Several techniques currently exist for constructing turbine wheel hubs having such dual properties. One technique includes forming a disk preform having a hub and a rim formed of alloys having different properties. For example, the hub may comprise a first alloy capable of exhibiting a first set of properties, while the rim may comprise a second alloy capable of exhibiting a second set of properties. In this case, the two alloys may be joined by a diffusion heat treatment, extrusion or another manner. In another example, the disk preform may initially have a first grain structure, and specialized equipment may heat an outer periphery of the disk preform to obtain a second grain microstructure. Although the aforementioned processing techniques yield high quality disks, only one disk may be produced at a time from each preform. Additionally, the techniques may not be suitable for forming parts meeting a particular quality standard or for producing relatively smaller-diameter components, such as disks for auxiliary power units.
Accordingly, it is desirable to have an improved method for forming a dual microstructure component. In addition, it is desirable for the improved method to be relatively inexpensive and simple to perform. Moreover, it is desirable for the improved method to be capable of producing dual microstructure components that may be used in relatively smaller-diameter components, such as auxiliary power units. Furthermore, other desirable features and characteristics of the inventive subject matter will become apparent from the subsequent detailed description of the inventive subject matter and the appended claims, taken in conjunction with the accompanying drawings and this background of the inventive subject matter.